When you switch on your equipment, the power supply components, tubes and transformers are in a discharged or a cold state. At the very moment of power application, the instantaneous current may be greater than ten times the normal running current for that unit. This high current places a strain on parts in the unit, particularly the power supply.
Using a 100-Watt light bulb as an example, the measured cold resistance is 10 Ohms. At the moment of power application, the initial current for this lamp is greater than 14 Amps, even though the average current is 1 Amp! fourteen times the current translates to 1440 Watts for that instant. It's no wonder that most electronics fail during a power on cycle.